Function is_write_outcome_definitive_http_status 

pub fn is_write_outcome_definitive_http_status(status: u16) -> bool

Returns true for non-JSON-RPC HTTP statuses where a state-changing write failed before the matching engine could accept it.

HTTP 4xx responses come from gateway, auth, throttling, or request-shape rejection paths. They are definitive for submit/cancel/modify outcomes, even when an idempotent read would retry some of them. HTTP 5xx and transport failures remain ambiguous for writes.

Retained for the HTTP order-write path (the execution client now writes over the WebSocket and classifies outcomes via is_write_outcome_ambiguous_ws).